Atrial and ventricular functional mitral regurgitation: prevalence, characteristics, outcomes, and disease progression

AIMS: Limited data exist on the natural history of functional mitral regurgitation (FMR), including atrial (AFMR), ventricular (VFMR), and dual FMR. This study examined the prevalence, characteristics, outcomes, and progression of these FMR subtypes. METHODS AND RESULTS: Consecutive patients with ≥mild to moderate FMR were included and classified as AFMR, VFMR, or dual FMR. AFMR is characterized by left atrial enlargement, while VFMR involves left ventricular enlargement or reduced left ventricular ejection fraction. Dual FMR combines features of both. Clinical outcome was all-cause mortality and heart failure (HF) hospitalization. Echocardiographic outcome was the progression from mild-moderate/moderate to severe FMR and from AFMR/VFMR to dual FMR. Of 22 814 patients, AFMR, VFMR, and dual FMR were identified in 39%, 14%, and 47%, respectively. Most (84%) had mild-moderate to moderate FMR. Over a median clinical follow-up of 4.7 years, dual FMR has the highest risk of all-cause mortality and HF hospitalization. Compared with AFMR, patients with VFMR have a higher incidence of all-cause mortality (adjusted HR = 1.73, 95%CI 1.54-1.94, P < 0.001) and HF hospitalization (adjusted HR = 1.23, 95%CI 1.15-1.32, P < 0.001). In the serial cohort with 2.4 (1.0-4.9) years echocardiogram follow-up, VFMR was associated with a 1.51-fold and 3.08-fold increase in the risk of progressing to severe FMR and dual FMR than AFMR (both P < 0.001). Sensitivity analyses did not change these findings. CONCLUSION: AFMR and VFMR have significant differences in survival and disease progression. Dual FMR is a common and distinct disease process that occurs in the progression of AFMR or VFMR and is associated with a poor prognosis.